Boiler-feeding apparatus



Nov. 17 1925- 1,561,675

J. G. WEIR BOILER FEEDING APPARATUS Filed March 10. 1924 Patented Nov. 17, 1925 UNITED STATESPATENTOFFICE.

TAM-ES GEORGE WEIR .OF CATHCART, GLASGOW, SCOTLAND; ASSIGNOR TO G. & J. WEIR, LIMITED,OF CATI-ICART,- GLASGOVRSCOTLAND.

BOILER-FEEDING APPARATUS.

Application filed March 10, 1924.; Serial Noe-698,326.-

ToaZZ whomz't may concern:

Be it known that LJaixrns GEORGE WEIR, a subject of the King of Great Britain, and residing at Cathcart, Glasgow, Scotland, have invented certain new and useful Improvements in Boiler-Feeding Apparatus; andvI do'hereby declare the following to be a full clear, and exact description of the invention, such as will enable others'skilled in the art to whichit appertains to make and use the same, reference being had to the accompanying drawing, and to -letters or fig-s ures of reference marked thereon, WlllGll form a part of this specification.

Electrically-driven centrifugal boiler feed pumps as commonly ,.used are unsatisfactory owing-to thepractically constant speed of the driving motor. This results in a wide variation of feed pressure at the boiler between full load and light load conditions. The feed pressure is also incapable of easy adjustment to suit the variation in conditions which generally occurs when the plant is running. On the other hand electricallydriven feed pumps are convenient and are in general more economical in power cost than steam pumps.

The present invention consists in a combination of apparatus for boiler feeding purposes. The invention will be described in the following specification and defined in the annexed claims.

In the drawings Figure 1 illustrates diagrammatically the carrying of the invention into efi'ect, in one convenient manner; and,

Figure 2 is a detail view of a modification thereof.

a is a variable-speed pump driven by a steam turbine 79. This pump is arranged in series with a constant-speed pump 0 to which it discharges by the pipe 0*. The pump 0 is driven by an electric motor cl. This electrically-driven pump is arranged to produce under no-load conditions a pressure diflerence between its suction and discharge of somewhat less than the full boiler pressure. The steam-driven pump, which is placed hetween the feed water supply a and the electrically driven pump, has its steam supply which is conveyed to it by the pipe t-controlled by a pressure-operated valve f. This valve is connected up by the pipe h with the pipe m through which the electrically driven pump delivers into the boiler feed pipe 41.

The valve isqactuatedby the pressure of discharge ofthe electrically-driven pump and is so loaded that steam is supplied to the steampump; whenever the discharge pressure of the electrically-driven pump falls below a given value. The steam pumpthen star-ts .(or accelerates) and imposes sufiicicnt pressure on the suction of the electricallydriven pump to raise the discharge pressure of the latter to the desired value. Thusthe steam pump. acts in such a manner that it augments the pressure generated by the electrically-drliven pump to the pressure de- This pressure may sired inthe feed pipe. be constant or variable. The work which the steam pump will be called upon to do willjtheretore depend inter alia on the frictional resistance in the feed pipe and on the characteristics of the electrically-driven pump under varyingloads.

The pipe It might be connected up to the feed pipe 01. instead of to the pipe m'.

The individual advantages ap'pertainin to the two types of pump are thus conserved in the combination.

A further and important advantage of this combination lies in the fact that the steam-driven pump may be arranged to act as a water-extraction pump, i. e. to draw the feed water directly from the condenser. In this case 0 represents the condenser (diagrammatically). Such an employment of the pump a enables the feed circuit to be arranged as a closed system.

A. further advantage lies in the fact that a steam-driven pump may be inserted in existing installations where an electricallydriven feed pump (or pumps) is already installed.

A steam-driven pump may be employed as hereinbefore described in the feed circuit where a plurality of electrically-driven constant speed pumps are used in parallel.

When the variable-speed pump is employed as above mentioned) as a waterextraction pump and when it is controlled by action on its steam supply valve, e. g. the valve f in the figures, a bypass S as shown in Figure 2 may be provided to this valve so that, even when the pressure in the feed pipe into which the constant-speed pump delivers is the maximum or the full amount desired, sufiicient steam is supplied to the water-extraction pump to permit it to withdraw water from the condenser and dis charge it at a pressure slightly in excess of atmospheric pressure.

In all cases in this specification Where the expression constant-speed has been used, it is to be understood that the speed is not necessarily absolutely constant but is approximately or practically constant.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is 1. The combination with a feed pipe for boilers of a constant-speed pump, a variablespeed pump arranged in series with, and on the suction side of, the said constant-speed pump and co-acting with it to deliver feed water into the said feed pipe, and means whereby the said variable-speed pump is controlled by the pressure in the said feed p1 )e.

2. The combination with a feed pipe for boilers of a constant-speed pump, a variable speed pump arranged in series with, and on the suction side of, the said constant-speed pump and co-acting with it to deliver feed water into the said feed pipe, a steam engine which drives the said variable-speed pump, and means whereby the said variable-speed pump is controlled by the pressure in the said feed pipe.

3. The combination with a feed pipe for boilers of a constant-speed pump, a condenser, a variable-speed pump arranged 1n series with, and on the suction side of, the

said constant-speed pump, and arranged to withdraw water from the said condenser, and arranged to co-act with the said constant-speed pump to deliver feed Water into the said feed pipe, a steam engine which drives the said variable-speed pump, means whereby the said variable-speed pump is controlled by the pressure in the said feed pipe, and means whereby suflicient steam is always supplied to the said steam engine to permit it to withdraw water from the said condenser and discharge it at a pressure slightly in excess of atmospheric pressure.

l. The combination with a feed pipe for boilers of a constant-speed pump, a directcurrent electric motor which drives the said pump, a variable-speed pump arranged in series with, and on the suction side of, the said constant-speed pump and co-acting with it to deliver feed water into the said teed pipe, and means whereby the said variable-speed pump is controlled by the I pressure in the said feed pipe.

I hereby sign my name to this spec1fication.

JAMES GEORGE WEIR. 

